[Kidney involvement in systemic necrotizing vasculitis]

Renal involvement occurs in 75% of the patients with systemic necrotizing small-vessel vasculitis ie microscopic polyangiitis, Wegener's granulomatosis or Churg-Strauss syndrome. Small-vessel vasculitis may also be limited to the kidney. The hallmark of small-vessel pauci-immune vasculitides consists of necrotizing glomerulonephritis and resultant crescent formation, without immune-complex deposits in vessel walls. The resulting renal manifestations consist of haematuria, proteinuria and rapidly progressive renal failure. ANCA testing has a 90% sensitivity for renal-associated pauci-immune small-vessel vasculitis. Kidney biopsy is required for demonstrating necrotizing vasculitis. Early identification and prompt treatment are mandatory to avoid early mortality and end-stage renal failure. Induction therapy combines corticosteroids and IV cyclophosphamide. Plasma exchange in indicated in the patients presenting with active renal lesions and serum creatinine > 500 micromol/L. Maintenance of immunosuppressive therapy is required for 18 months. Twenty to 50% of the patients relapse during follow-up, and close monitoring is warranted for early detection.